A man wears a mask on Tiananmen Square in thick haze in Beijing Tuesday. Extremely high pollution levels shrouded eastern China for the second time in about two weeks Tuesday, forcing airlines in Beijing and elsewhere to cancel flights because of poor visibility and prompting government warnings for residents to stay indoors. (Ng Han Guan/AP)

Since January began, a nasty brew of gray and brown smog has commandeered Beijing’s air on multiple occasions, deeply compromising its air quality and slashing visibility.

CNN says you can see less than 200 feet in front of you in some spots.

Wire reports indicate air pollution levels have mostly varied between very unhealthy and hazardous over the last two weeks.

“On Tuesday, [the pollution] hit 517 on an index maintained by the U.S. Embassy in Beijing, which described the pollution as “Beyond Index”,” Reuters reported.

The Associated Press (AP) noted that PM2.5 (small particulates in the air, known to be hazardous) levels reached 526 micrograms, which is more than 20 times worse than safe levels set by the World Health Organization

Satellite image of Beijing smog on January 14. Via NASA: “The brightest areas tend to be clouds or fog, which have a tinge of gray or yellow from the air pollution. Other cloud-free areas have a pall of gray and brown smog that mostly blots out the cities below.” (NASA)

Two weeks ago, the PM2.5 level was even higher at 886 micrograms the AP said. One Washingtonian doing business in Beijing at the time described “tasting” the air pollution:

“For the first time I can remember [having traveled to China almost annually since 1992], I could actually taste the air when I breathed,” the traveler said. “It was faintly sweet and quite unsettling when I thought about it. I was nervous about breathing too deeply and I found myself getting tired walking for I was purposefully only taking very shallow breaths.”

The air pollution has led to a “surge in respiratory illneses” according to China Daily. It reports: “A pediatric hospital in downtown Beijing has treated a record 9,000 children this month, mostly flu, pneumonia, tracheitis, bronchitis and asthma patients.”

The current spell of air pollution has reached off-the-chart levels despite government efforts to curb smog levels by temporarily shutting down 103 polluting factories Reuters reported.

A grass-root lobbying effort for more aggressive clean air measures is gaining traction reports Yale’s Environment360 blog:

... an online poll has found overwhelming support for new clean air legislation. Ten hours after real estate mogul Pan Shiyi posted the poll on the popular social media platform Sina Weibo, 99 percent of respondents — more than 32,000 people — agreed that the government should enact a Clean Air Act, with many users offering specific measures to curb pollution, including car-free days during smoggy periods, stricter auto emissions standards, and public health protections.

Because winds are forecast to remain light around Beijing, the smog is expected to persist in the stagnant air for the next couple of days.

Related: The killer London smog event of December, 1952: a reminder of deadly smog events in U.S.